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This study investigates the impact of Rib/Channel dimensions, heat and water transport on cell performance under high current density in PEMFCs, and evaluates the limiting current density using a multiphase mixture model.

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What they did

System
MFC

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Abstract

Proton exchange membrane fuel cells (PEMFCs) are regarded as a promising alternative clean power source for automotive applications. Key to the acceptance of PEMFCs for automobiles are cost reduction and power density for compactness. In order to meet these requirements, further improvement of cell performance is required. In particular, under higher current density operation, water and heat transport in PEMFC have strong effects on cell performance. In this study, the impact of Rib/Channel dimensions, heat and water transport on cell performance under high current density is investigated using the multiphase mixture model (M2 model), and the limiting current density is evaluated using a uniform test cell with 10cm² active area and 24 straight channels. Limiting current densities were measured under different oxygen concentrations at 70°C and 70% relative humidity at both sides. In order to neglect the effect of liquid water in channels and the distribution of oxygen and hydrogen concentrations along the flow channel, large flow rates were introduced at both sides. Experimental results show a nonlinear relation between oxygen concentration in the channel and limiting current density. Numerically it is found that this nonlinear trend is caused by liquid water in the Rib region. In addition, it is also found that not only liquid water, but also heat transport and water transport through the membrane significantly affect the limiting current density. Finally, it is concluded that the combination analysis using limiting current experiments of uniform cell system and M2 model is very useful for fundamental understanding and for fuel cell design optimization.

Key findings

  • Limiting current densities were measured under different oxygen concentrations at 70°C and 70% relative humidity.
  • A nonlinear relation was found between oxygen concentration in the channel and limiting current density.
  • The study suggests that water and heat transport have strong effects on cell performance under high current density operation.

Keywords

Limiting currentProton exchange membrane fuel cellCurrent densityCurrent (fluid)Power densityWater transport

Identifiers

DOI
10.1115/fuelcell2008-65201
Journal
ASME 2008 6th International Conference on Fuel Cell Science, Engineering and Technology
Year
2007